Skin is subject to abuse by many extrinsic (environmental) factors as well as intrinsic factors. A common extrinsic factor is exposure to ultraviolet radiation. Whether extrinsic or intrinsic, the abuse results in skin aging. Skin aging happens in two ways: (1) through the natural aging process which dermatologists call chronological aging (also known as chronoaging); and (2) through UV rays in sunlight accelerating the aging process which dermatologists call photoaging. Chronoaging results in thinning, loss of elasticity and general degradation of skin. As the skin naturally ages, there is a reduction in the cells and blood vessels that supply the skin. There is also a flattening of the dermal-epidermal junction which results in weaker mechanical resistance. As a consequence, older persons are more susceptive to blister formation in cases of mechanical traumas or disease processes (Oikarinen et al., Photodermatal. Photoimmunol. Photomed., 7:3-4 (1990)).
By contrast, photoaging, or premature aging, is a process in which the skin changes in appearance as a result of repeated exposure to sunlight. Typically, photoaging occurs in areas of habitual exposure, such as the scalp, face, ears, neck, chest, forearms and hands. The changes associated with photoaging include elastosis, atrophy, wrinkling, vascular changes (diffuse erythema, ecchymoses, and telangiectasias), pigmentary changes (lentigines, freckles, and areas of hypo- and hyper-pigmentation), and the development of seborrheic keratosis, actinic keratosis, comedones and cysts.
Antioxidants are useful agents treating the skin from damage caused by chronoaging and photoaging. The most useful antioxidants are those that provide the highest capacity to absorb free radicals. The oxygen radical absorbance capacity (ORAC) is a measurement of this (Dreher F, Maibach H. Curr Probl Dermatol. 2001; 29:157-64.) Anthocyanins are a type of antioxidants that generally encompass a class of flavonoid compounds that are naturally occurring, water-soluble compounds, responsible for the red, purple, and blue colors of many fruits, vegetables, cereal grains, and flowers. Most anthocyanins have a high ORAC rating compared to other antioxidants and make them particularly useful for their topical antioxidative properties. Additionally, anthocyanins are collagenase inhibitors, which helps in the prevention and reduction of wrinkles, increase in skin elasticity, etc., which are caused by a reduction in skin collagen.
For ripe berries, a rich source of anthocyanin antioxidants, there is generally a linear relationship between ORAC values and anthocyanin content. High ORAC ratings are generally defined as greater than 25 μmole of Trolox equivalents (TE)/g. In most fruits, ORAC values ranged from 7.8 to 33.7 μmole TE/g of fresh berries and the ORAC values of the leaves range from 69.7 to 182.2 μmole TE/g (Wang S Y, Lin H S., J Agric Food Chem. 2000 February; 48(2):140-6). Comparatively, a fruit with an ORAC value of 8 μmol TE/g of fresh berries will have an ORAC value of about 35 μmol TE/g of dried berries and an ORAC of 34 μmol TE/g of fresh berries corresponds with an ORAC of 162 μmol TE/g dried matter. Black raspberries have a very high ORAC of 77 μmole TE/g while boysenberries have an ORAC of 48 μmole TE/g, and red raspberries and blueberries have an ORAC of 24 and 23 μmole TE/g, respectively. (http://www.deckerfarm.com/antioxidants.html). Acai is another fruit having a high ORAC content (167 ORAC units/g according to Brunswick Laboratories). Other fruit having high ORAC values include pomegranate (33.1 μμμmole TE/g) and aronia berry (62 μμmole TE/g) as well as whole coffee fruit extract (6250 ORAC units per gram according to Brunswick Laboratories). The stage at which the plant is harvested affects the ORAC value. Blackberries have their highest ORAC values during the green stages, whereas red raspberries have their highest ORAC values when ripe. The ORAC may be obtained by using the method described by the U.S. Department of Agriculture's Agricultural Research Service (Prior and Cao, 83(4) J. AOAC INT. 950-6 (2000)). Additionally, testing for ORAC, H-ORAC, N-ORAC, S-ORAC, and ORAC-E (high throughput ORAC for oil-in-water emulsion) is available from Brunswick Laboratories (www.brunswicklabs.com).
Anthocyanins have been formulated in topical form. For example, U.S. Pat. Pub. 2004/0022818 provides a skin care composition comprising fruit particles. Red and blue fruits, as well as other fruits which contain anthocyanins are included in this composition. Similarly, U.S. Pub. 2003/0161897 and U.S. Pat. No. 6,361,786 provide a topical antimicrobial factor having fruit juice (cranberry, Aronia berry, blackberry, grape or blueberry) and polyvinylprolidinone. A topical oil-in-water emulsion containing a surfactant/emulsifier and a lipid, which may be an anthocyanin-containing berry extract, is provided by WO 98/05294. U.S. Pat. No. 5,011,855 provides a cosmetic composition having a-linolenic acid and an oil extracted from Ribes genus fruits.
However, there are problems associated with these and other uses of antioxidants in a topical formulation. Particularly, antioxidants are readily oxidized and lose their anti-oxidant capacity. Additionally, some of the oxidation products of antioxidants will have a deleterious effect; for example, vitamin C oxidizes to dehydroascorbate which is known to lead to the formation of advanced glycation endproducts (AGEs) and therefore increase the signs of aging skin.
Therefore, a topical formulation containing an antioxidant with a much higher ORAC and consequently greater anti-oxidant power is needed in combination with a formulation that protects the antioxidant from degradation and loss of the anti-oxidative power to be used in treating and protecting the skin.